Prayer (Kitab Al-Salat): Details of Commencing Prayer
Dawud :: Book 3 : Hadith 887
Narrated Anas ibn Malik:
I did not offer behind anyone after the Apostle of Allah (peace_be_upon_him) a prayer like the prayer offered by the Apostle of Allah (peace_be_upon_him) than this youth, i.e. Umar ibn AbdulAziz. We estimated reciting glorification ten times in his bowing, and in his prostration ten times.